In the conventionally-known front vehicle body structures, a front side frame extends in a front-rear direction of the vehicle body, a lower member is disposed laterally outward (i.e., outward in a vehicle width direction) of the front side frame and extending substantially parallel to the front side frame as viewed in plan, an inner bumper beam extension is disposed at the distal end of the front side frame, an outer bumper beam extension is disposed at the distal end of the lower member, and a bumper beam extends in the vehicle width direction and connected to the respective distal or front ends of inner and outer bumper beam extensions.
An example of the front vehicle body structures is disclosed in Japanese Patent Application Laid-open Publication No. 2010-83448 (hereinafter referred to as “patent literature 1”), according to which, even when there has occurred a narrow offset collision where a frontal collision load (i.e., impact load applied from the front of the vehicle) acts on a narrow range of a laterally outer end portion (i.e., outer end portion in the vehicle width direction) of the vehicle.
However, the front vehicle body structure disclosed in patent literature 1 includes no means for positively transmitting a frontal collision load, acting on the outer bumper beam extension and lower member, for example from the lower member to the front side frame. Thus, when a narrow offset collision has occurred, the frontal collision load would be received by members disposed laterally outward of the side frame, and thus, an impact absorbing capability would be considerably limited.
Further, in the front vehicle body structure disclosed in patent literature 1, the outer bumper beam extension has a smaller length than the inner bumper beam extension. When an offset collision has occurred within a range including the front side frame, for example, the outer and inner bumper beam extensions can take part in absorption of a frontal collision load. However, when a narrow offset collision has occurred only within a narrow range laterally outward of the front side frame, it would be difficult for the inner bumper beam extension to take part in absorption of a frontal collision load. Therefore, it is preferable that the outer bumper beam extension is constructed to have an increased impact absorbing capability.
Further, in the front vehicle body structure disclosed in patent literature 1, the outer and inner bumper beam extensions are provided separately with a poor interconnection therebetween. Thus, when a frontal collision acts on the outer bumper beam extension, it would be difficult for the inner bumper beam extension to take part in impact absorption. Furthermore, in the front vehicle body structure disclosed in patent literature 1, a distal end portion of the front side frame has a width increasing toward the front of the vehicle body as viewed in plan, and thus, a space between the front side frame and the lower member is so small that it would be difficult to mount other component parts within the space. Besides, a mold for forming the front side frame has to have an increased size, and a yield rate of the front side frame would decrease.
Further, Japanese Patent Application Laid-open Publication No. 2010-83453 (hereinafter referred to as “patent literature 2”), for example, discloses a front vehicle body structure which includes inner bumper beam extensions extending forward toward the front of the vehicle body from the respective front ends of the left and right front side frames and outer bumper beam extensions extending forward toward the front of the vehicle body from the respective front ends of left and right upper members. More specifically, the front vehicle body structure disclosed in patent literature 2 includes: the left and right front side frames disposed on left and right sides of the vehicle body and extending in the front-rear direction of the vehicle body; left and right upper members disposed upward and laterally outward (i.e., outward in the vehicle width direction) of the left and right front side frames and extending obliquely forward and downward from the left and right upper front pillars; the left and right inner bumper beam extensions extending forward from the respective front ends of the left and right front side frames; the left and right outer bumper beam extensions extending forward from the respective front ends of the left and right upper members; and a bumper beam extending in the vehicle width direction between the left and right outer bumper beam extensions and joined with the left and right inner bumper beam extensions and the left and right outer bumper beam extensions.
When there has occurred a narrow offset collision where a frontal collision load acts on a narrow range of a laterally outer end portion (i.e., outer end portion in the vehicle width direction) of a front section (bumper beam) of the vehicle, the frontal collision load is transmitted from the bumper beam to the left and right inner and outer bumper beam extensions. These bumper beam extensions can absorb the impact by collapsing due to the frontal collision load.
Generally, during travel of a vehicle, various external force acts on the vehicle body depending on states of the travel. For example, depending on a posture of the traveling vehicle, twisting force may act on the left and right front side frames and the left and right upper members. In order to increase steering stability of the vehicle, it is required to increase rigidity, particularly rigidity against twisting force (i.e., twisting rigidity), of laterally outward end portions of a front section the vehicle body. However, increasing the rigidity of the laterally outer end portions of the front section of the vehicle body cannot secure sufficient impact absorbing performance at the time of occurrence of a narrow offset collision involving a frontal collision load.